CBSE 12th

it's totally depends upon the company. Many companies ask for throughout 60% or first division but most of the company focus on only mba grade sheet or sometimes on under graduate marks too but you should don't worry much about ur marks.

It is good to get more than 75 percentile in cat to be on safer side to get admission.

A minimum of 75 percentile is required for a OBC category to get admission in. Any work experience less than 12 months never matters in your selection process

You will need above 75% so that you have a better chance to get placed in a good college or in a top NIT.

Yes, you should take up architecture if you love travelling because in order to understand architecture, you have to visit the best architecture buildings which needs you to travel. Also, you have to do case studies on different architects as your academic curriculum activity to understand the concepts. You also require to travel a lot for it. Thus, architecture is the best option for you.

You can wither plan of pursuing B.Com and MBA otherwise can also think about pursuing CA and CS.

Yes, you can pursue it from UP board.

For any NIT, you required above 180 marks in JEE mains.
Best of luck.